Experimental extraction of the quantum effective action for a non-equilibrium many-body system

Finding self-similar behavior in quantum many-body dynamics via persistent homology

“…Myriad of interesting further applications of persistent homology within QFT exist. With regard to the recent experimental progress in handling ultracold quantum gases to simulate quantum dynamics [22,23,31]: What can we learn from a thorough persistent homology analysis of experimental data, including the investigation of different filtration functions? Can relative homology groups give new geometrical insights into the relevant physical processes?…”

“…While there are many different ways of driving a Bose gas away from equilibrium, it has recently been demonstrated experimentally that the subsequent relaxation dynamics can exhibit universal properties that are insensitive to the details of the initial conditions and system parameters [22][23][24]. Theoretical results based on field correlation functions indicate that vastly different systems far from equilibrium may share very similar universal scaling properties, ranging from post-inflationary dynamics in the early universe [25,26], and ultrarelativistic collision experiments with heavy nuclei [27][28][29], to ultra-cold quantum gases in the laboratory [30,31]. In particular, quantum as well as classical statistical field theories appear to belong to the same nonthermal universality class [32].…”

QCD thermalization: Ab initio approaches and interdisciplinary connections

“…While digital quantum simulations based on a Trotterized time evolution on a universal quantum computer are challenging to scale up, present large scale analog quantum simulators using ultracold quantum gases already explore the many-body limit described by quantum field theory [54,55,[647][648][649][650][651][652][653][654][655][656][657][658][659][660][661][662][663]. In principle, with quantum simulators non-universal aspects of the dynamics of gauge theories can be studied.…”

“…For instance, in Refs. [54,662] the non-equilibrium dynamics of magnetic hyperfine excitations of a spin-1 Bose gas was studied in an elongated trap, following a sudden change in the applied magnetic field as an external control parameter. Figure 32 exemplifies the scaling dynamics of the measured transversal spin for three different initial conditions.…”

Constructing Field Theories Using Quantum Simulators

“…This successful benchmark now paves the way to studying more complex cases. Future work might attempt to solve sine-Gordon models in the regime of strong quantum correlations; improve the description of the superfluid-insulator transition, for which recent experiments revealed that the QFT parameters need to be revised [7]; and tackle nonequilibrium problems [8]. More generally, this work shows a new benefit of quantum simulators: Instead of just finding the physical behavior of a specific model, they can now be used to build and refine field theories that may be applicable not only to the system considered by the authors but also to a whole spectrum of many-body problems.…”